<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>play canvas</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    html,body{
      height: 100%;
      width: 100%;
      position: relative;
      text-align: center;
    }
    .canvas{
      border: 2px solid skyblue;
      position: absolute;
      display: block;
      top: 50%;
      left: 50%;
      transform:translate(-50%,-50%);
    }
  </style>
</head>
<body>
  <button class="btn">click me</button>
  <canvas class="canvas" id="canvas" width="500" height="500"></canvas>

  <script src="scripts/util/tool.js"></script>
  <script src="scripts/index.js"></script>
</body>
</html>